Image Forming Apparatus and Method

Abstract

In an image forming apparatus including plural exposure units each deflecting a light beam from a light source by means of an oscillation mirror in resonant oscillations and scanning the deflected light beam on a latent image carrier thereby forming a latent image on the latent image carrier, every one of the exposure units assuredly attains an adequate amplitude of the oscillation mirror for ensuring the formation of images of high quality. More specifically a CPU 101 retrieves resonant frequencies of individual deflectors previously stored in a memory. The CPU 101 calculates an average value of these resonant frequencies and applies a drive command to mirror drivers 1022 of the exposure units 6 Y, 6 M, 6 C, 6 K such as to drive all the deflectors into oscillations at the average value. Alternatively, a resonant-frequency adjusting section 653 makes adjustment to match the resonant frequencies of the individual deflectors substantially with a drive frequency. This ensures that all the oscillation mirrors attain adequate amplitudes.

1 . An image forming apparatus comprising:
 a plurality of latent image carriers;   a plurality of exposure units each provided in correspondence to the respective latent image carriers, each of the exposure units including a light source and an oscillation mirror, and forming a latent image on the latent image carrier by deflecting a light beam from the light source into a deflected light beam by means of the oscillation mirror in oscillations and scanning the deflected light beam on the latent image carrier;   a drive unit which applies a drive signal having one drive frequency to each oscillation mirror to drive the oscillation mirror at the drive frequency; and   a controller which controls the drive unit,   wherein the drive unit is arranged to be capable of varying the drive frequency of the drive signal, and   wherein the controller determines an optimum value of the drive frequency based on each resonant frequency of the oscillation mirrors and controls the drive unit in a manner to match the drive frequency of the drive signal substantially with the optimum value.   
   
   
       2 . An image forming apparatus according to  claim 1 , further comprising a storage unit which stores the resonant frequencies,
 wherein the controller retrieves the resonant frequencies from the storage unit to determine the optimum value of the drive frequency based on the retrieved resonant frequencies.   
   
   
       3 - 6 . (canceled) 
   
   
       7 . An image forming method comprising:
 a preparing step of preparing a plurality of latent image carriers each formed with a latent image on its surface;   a latent image forming step of deflecting a light beam from a light source by means of an oscillation mirror oscillating at a predetermined drive frequency and scanning the deflected light beam on each latent image carrier;   a developing step of developing the latent images with different color toners, respectively, thereby forming a plurality of toner images having different colors each other;   a transferring step of superimposing the different color toner images on a transfer medium thereby forming a color image; and   an adjusting step, performed prior to the latent image forming step, of determining an optimum value of the drive frequency based on each resonant frequency of the oscillation mirrors so that each oscillation mirror starts oscillation at the optimum value.   
   
   
       8 - 12 . (canceled) 
   
   
       13 . An image forming apparatus according to  claim 1 , wherein the drive unit comprises a plurality of drivers each provided in correspondence to the respective oscillation mirrors, each of the drivers applying the drive signal to the oscillation mirror to drive the oscillation mirror. 
   
   
       14 . An image forming apparatus according to C  claim 1 , wherein the drive unit comprises a plurality of drivers each provided in correspondence to the respective oscillation mirrors, each of the drivers applying the drive signal to the oscillation mirror to drive the oscillation mirror. 
   
   
       15 . An image forming apparatus according to  claim 13 , further comprising a plurality of amplitude detectors each provided in correspondence to the respective oscillation mirrors and detecting an amplitude of the oscillation mirror,
 wherein the drivers adjust amplitudes of the oscillation mirrors based on outputs of the amplitude detectors, respectively.   
   
   
       16 . An image forming apparatus according to  claim 14 , further comprising a plurality of amplitude detectors each provided in correspondence to the respective oscillation mirrors and detecting an amplitude of the oscillation mirror,
 wherein the drivers adjust amplitudes of the oscillation mirrors based on outputs of the amplitude detectors, respectively.